Depth profiling of taxol-loaded poly(styrene-b-isobutylene-b-styrene) using Ga+ and C60+ ion beams

The surface of a triblock copolymer, containing a solid-phase drug, was investigated using 15 keV Ga+ and 20 keV C60+ ion beams. Overall, the results illustrate the successful use of a cluster ion beam for greatly enhancing the molecular ion and high-mass fragment ion intensities from the surface and bulk of the polymer system. The use of C60+ also established the ability to see through common overlayers like poly(dimethyl siloxane) which was not possible using atomic ion sources. Moreover, the use of C60+ allowed depth profiles to be obtained using primary ion dose densities in excess of 6 × 1014 C60+/cm2. Resulting sputter craters possess relatively flat bottoms without the need for sample rotation and reached depths of ca. 2 μm. AFM results illustrate the more gentile removal of surface species using cluster ions. Specifically, phase contrast and topographic images suggest the relatively high ion doses do not significantly alter the phase distribution or surface topography of the polymer. However, a slight increase in rms roughness was noticed.